Saturday, September 24, 2022


RV Electricity – Just Ask Mike (J.A.M.): Be prepared for a converter/charger failure

By Mike Sokol

Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) with the subject line – JAM.

Dear Readers,

I’ve received several questions like this one in just the last week, so I think it’s a great JAM session. What do you do when your converter fails and the house batteries die?

Dear Mike,

I’m stuck at a campground and can’t get my hydraulic levelers to work or my slides to retract. Also the lights inside of the RV are really dim and my monitor panel says the battery is dead. How can that be since I’ve been plugged into shore power for days? – Stuck in Duck (NC) 

Dear Stuck in Duck,

Okay, there’s one basic tool you should never leave without, and one extra gadget which I think would be very useful to carry with you. Yes, I know you all say I carry too much, but many times I’ve been 3,000 miles from home solo and needed to make things work. So this is how I make things work.

First of all, everyone who travels in an RV needs a basic Digital Meter. They’re just too useful for troubleshooting any RV electrical system and can save you a ton of time (and money) in the long run. I like the inexpensive manual ones from Southwire and Klein which you can get at any big box store for $20 or so. Here’s a Southwire 10030S which is a great choice. If you don’t know how to use one, I have a number of articles on RVtravel that go over the basics. So now is a good time to start with something like this one. Read about it using a meter to measure a 12-volt battery HERE.

Secondly, if you’re RV can’t be packed up to leave without battery power for the levelers and slides, then you should consider carrying a simple 10-amp battery charger for your tow vehicle. Even this $50 one from Harbor Freight looks like it should do the job. They will have sales on these for a low as $40, so it won’t break the bank.

But first you need to determine if your converter/charger has failed. The best way to know is simply measure the DC voltage across the battery with the shore power connected and the circuit breaker feeding the converter/charger turned on. Set the meter to the 20 volt DC range, and place the red meter probe on the positive battery terminal, and the black probe on the negative battery terminal. If the battery measures something over 14 volts, then the charger part of your converter is working and it’s likely not the problem. So something else must be wrong. However, if you’re reading mid to low 12 volts across your house battery, then your RV converter/charger is no longer charging the batteries and they’ve discharged so low you can’t run anything that needs significant power.

moneyThe key thing to remember is that a service call from an RV technician is going to be expensive and could take days to schedule. What you really need to do is get your RV batteries charged up so you can pull up your levelers, pull in your slides, and get on the road. Then you can troubleshoot the converter/charger at the leisure after you get home.

All you have to do is connect the red alligator clip to the 12-volt positive terminal on the battery (or batteries) and the black alligator clip to the negative terminal of the battery or batteries that’s connected to the RV chassis ground. It’s super simple with 12 volt batteries and only a little more complicated with a pair of 6 volt batteries in series.

A 10-amp charger should bring up a dead battery to half-charge in about 5 hours or so, maybe less. And that should easily be enough power to get your RV properly retracted for a homeward journey.

OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.

Let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at For more info on Mike’s qualifications as an electrical expert, click here.
Join Mike’s popular and informative Facebook group.
And you don’t want to miss Mike’s webcasts on his YouTube channel.

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11 months ago

In the middle of 3 days of 100 degree temperatures, our converter died. We had a 89 mile trip each way to the nearest RV tech or parts stores, none of whom had anything other than inverters. (Not useful).

I had to pull a converter out of a dumped travel trailer in the closest town and say a prayer it would fit, still worked and that I could figure it out. I ordered a new one online – 10 days before it would arrive.

After hours of research, prayers, I retrieved the used converter, disconnected our hardwired 15 year old version and installed the new/used one. It WORKED! I don’t know who was more amazed – me or my husband. But we had lights and air conditioning and our dogs were safe. Bottom line is as full timers, you need to learn everything you can about how your RV actually works – you never know what will happen.

2 years ago

That should work unless one of the batteries has developed an internal short, then it will not charge or be able to be jumped. Rare.

Vanessa Simmons
2 years ago

Mike, I just had a thought! (people tell me that is dangerous!) I have several of those battery jump starters in vehicles and RV. Could that be hooked up somehow to give enough power to pull in the slides, etc?

By the way I highly recommend people carry one of these. I have used them to jump start my vehicles so many times and have had only one truck that it wouldn’t start when helping out someone. That was an F-250 that even when connected to a Chevy truck wouldn’t start without lots of jimmying it around.

2 years ago

If you’re struggling for article content, simple tips like this one on a one page printable that could be stored in camper would be awesome!

2 years ago

I’ve had issues with dead batteries and a charger failure where the charger was stuck in bulk mode and cooked my batteries. I started using an INNOVA 3721 Battery and Charging System Monitor that plugs into the cigarette lighter outlet on the dash. It is always on, so it makes it easy to keep an eye on battery voltage.

Bill Turkus
2 years ago

I mount a battery charger in the battery box. It has a digital readout to tell me if the battery is fully charged. I plug the charger into an extension cord to the 20 amp outlet on the pedestal. I also installed a 4 way shut off so that I can prevent the batteries from discharging when I am not using them.

2 years ago

I have two 6 volt house batteries. What is the connection for that scenario?

Tom R
2 years ago
Reply to  Ray

Look at the illustration above Mike’s picture at the end of the article.
comment image

2 years ago

Good information. One note, always attach the 12v cables BEFORE plugging in the charger. Any sparks near a battery could cause an explosion.

2 years ago

Mike, even though this isn’t my problem…yet…I want to thank you so much for telling me how to check this problem in a short, concise, easy-for-me-to-understand way. Sometimes your responses tend to get a little long-winded and too technical so I just skip over them. I realize there are people who want to know “all about” a particular problem or article, but sometimes just a “short and sweet” answer will suffice.

STEPHEN P Malochleb
2 years ago

Hey Mike, love the work you’re doing for the RV community. I carry a heavy duty dual battery jump pack with me. It has not only the jumper cables, but usb ports, and 2 110 volt outlets.
You can run tv’s, radios, and small power tools. It’s about the size of carry on luggage. It also comes in handy when someone needs a jump start. Just another back up power source.

Ron Brooks
2 years ago

Hi Mike. I really appreciate your expertise when it comes to electronics.I have sent several people from various chat rooms to your website when they post about electrical problems. Would the switch that links your house batteries to your chassis battery not back feed enough to power your slides and leveled jacks? I would make sure you start your motor first, and even get someone to rev the motor as you do it.

Mike Sokol
2 years ago
Reply to  Ron Brooks

Yes it should. But if you have a trailer an external charger is your only good option other than jumper cables.

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